Your task in physics laboratory is to make a microscope from two lenses. One len

Question

Your task in physics laboratory is to make a microscope from two lenses. One lens has a focal length of 3.2 , the other 1.5 . You plan to use the more powerful lens as the objective, and you want the eyepiece to be 18 from the objective.

The question asks in part one: For viewing with a relaxed eye, how far should the sample be from the objective lens?

In part one, I am having troubles finding what the image distance is for the first lens. I know 1/f=1/object distance + 1/image distance and that the image distance for the first lens is the object distance for the next. I guess I am having troubles applying this to the problem. In part one, I am having troubles finding what the image distance is for the first lens. I know 1/f=1/object distance + 1/image distance and that the image distance for the first lens is the object distance for the next. I guess I am having troubles applying this to the problem.

Explanation / Answer

Of the given focal lengths of the lenses, for the objective to have high power, the focal length of the lens should be smaller. So the focal length of the objective is 1.5 and focal length of the eyepiece is 3.2 - make note that units are not mention. so i'm working out with out units. Now for the normal relaxed eye, the distance of distinct vision is i2 = 25 So the image distance is 25 from the eyepiece. Using the thin lens equation          (1/f2) = (1/O2) + (1/ i2)          (1/3.2) = (1/O2) + (1/ 25)     Object distance for the second lens is        O2 = 3.67 Now the image distance of the objective lens is taken from the equation as           O2 = d - i1         i 1 = d - O2              = 18- 3.67              = 14.33 This is the image distance due to the objective lens. Now we use the same lens equation for the object distance of the objective lens is      (1/f1) = (1/O1) + (1/i1)       (1/1.5) = (1/O1) + (1/14.33) Object distance       O1 = 1.675   

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